RIVER LANDFORMS

Xon Vilahur i Godoy

Institut de Llagostera

RIVER-BASIN

 

A river basin is an area drained by a river and its tributaries. Other river features include:

Watershed, an area of higher land separating two drainage basins.

Source, the place where a river begin Tributary, a smaller river joining a large river Confluence, the place where two rivers join. Mouth, the place where a river enters in a

lake or the sea Streams or brooks are the names given to

small rivers Drainage pattern is the way rivers are

arranged on the landscape, the most commons ar, dendritic, parallel or radial.

http://techalive.mtu.edu/meec/module01/whatiswatershed.htm

UPPER COURSE: WATERFALLS AND RAPIDS

A waterfall is a place on a river where water flows vertically. Waterfalls are a common feature in the upper course of many large rivers. A waterfall occurs when a layer of hard resistant rock lies over a layer of softer rock, which will erode more easily.

 Rapids are a series of little waterfalls; these can be found where a waterfall has retreated, the hard rock layer is undercut causing the waterfall to move upstream. They are found where there are alternative bands of hard and soft rocks.

MIDDLE COURSE: FLOODPLAIN, MEANDERS AND OX-BOW LAKES  

Less steep gradient, lateral erosion, the river starts to meander.

Over time, the loop of a meander becomes tighter: the river cut across the neck of the meander to form a straight river channel and forms an ox-bow lake.

o Floodplains: area of flat land formed on either side of a river, combination of erosion and deposition :

Deposits of alluvium ( Fertile and good for farming and

agriculture. Floodplains are highly populated.

http://www.youtube.com/watch?v=8uV-BuBpIFw&feature=related

"http://www.libraryindex.com/pages/8308/meander.html">meander</a>

FLUVIAL TERRACES

Fluvial terraces : elongate deposits of sediments parallels to the sides of floodplains and fluvial valleys.

Remnants of earlier floodplains that existed at a time when a river was flowing at a higher elevation; then the stream has changed its elevation and has created a new floodplain.

Due to changes in the base level or in the volume of the fluvial flow (changes in climate: glaciations)

MOUTHS: DELTAS AND ESTUARIES

River channel deep and wide, large discharge

Valley, wide and flat, wide flood plain.

Deltas , deposits of alluvium, sand, silt and clay at the mouth of large rivers (Ganges, Nile, Ebre,…) in tideless seas.

The deposit of the river load occurs faster than the sea can remove the material.

Permanent land feature, rich in alluvium, fertile farmland.

 

ADJECTIVES: Large/ narrow long/short small/big deep/shallow wide/narrow fertile/sterile good/bad

MOUTHS: DELTAS AND ESTUARIES Estuaries: funnel-shaped

mouths. Mouth of a wide river when

its current is met by the tides.

Most are found where an existing river has had its lower reaches flooded ed river after changes in sea level.

In Galicia are called Rías, and in Norway are called Fjords

  

FLOODINGS

Flood : river that overflows its banks Causes: A rapid increase in discharge over a short period of

time, so the river system is unable to transport it away. Factors: Both human and physical factors Physical factors: prolonged rain or a short heavy rain storm,

snow melt which releases stored water; steep slopes, narrow valleys or impermeable rocks.

Human factors: Deforestation, construction of urban areas, changes of the natural course of the river.

FLOODINGS

Impacts: devastation, extensive damage, destruction of food supplies, buildings, farmlands, vehicles, transports, power and people.

Worse impact on LEDCs than on MEDCs. (emergency services, money, equipments, and poor communications in LEDCs make recovery more difficult.)

Benefits, deposits fine silt and sediment, which helps to fertilise the soil and generates excellent conditions for farming. Some LEDCs use river flooding to cover farmland with fertile alluvium and also to provide water for irrigation channels (e.g. Ganges in Bangladesh)

Prevention: prediction, prevention and control. Flood management to reduce the impact of flooding: river management, changing land use, dams and reservoirs...